Hairy Beggarticks (Bidens pilosa) is a dicot weed in the Asteraceae family. In Brazil this weed first evolved multiple resistance (to 2 herbicide sites of action) in 2016 and infests Corn (maize), and Soybean. Multiple resistance has evolved to herbicides in the Groups B/2, and C1/5. These particular biotypes are known to have resistance to atrazine, and imazethapyr and they may be cross-resistant to other herbicides in the Groups B/2, and C1/5.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

ABSTRACT Resistance to herbicides is a serious threat to crop production worldwide, especially in agronomic crops and cereals. This research evaluated the possible occurrence of Bidens pilosa resistant to imazethapyr and atrazine in Brazil. The resistant biotype was collected from an area with a history of repeated application of photosystem II (PSII) and ALS inhibitor herbicides. The susceptible biotype was collected from an area with no history of herbicide application. Resistance verification experiments were carried out in the greenhouse. The treatments were arranged in a 3 x 8 factorial scheme, where the first factor was populations [susceptible (S), parent resistant (PR), and resistant F1 (RF1)]; and the second factor was herbicide dose (0, 375, 750, 1500, 3000, 6000, 12000 and 24000 g ha-1 for atrazine; or 0, 12.5, 25, 50, 100, 200, 400 and 800 g ha-1 for imazethapyr). The resistance factor to atrazine was 2.83 for PR and 5.55 for RF1. This population was more resistant to imazethapyr (>21-fold) than it was to atrazine. The recommended maximum dose of the herbicides did not control this B. pilosa population adequately. The data support the claim that B. pilosa population from this field in Quarto Centenário, Parana is resistant to two herbicide modes of action - PSII inhibitor (i.e. atrazine) and ALS inhibitor (i.e. imazethapyr). This is the first report of such case for this species, globally. Cross-resistance to other ALS inhibitors and other PS II inhibitors as well as the respective mechanisms of resistance to each herbicide are being investigated.

Greenhouse, and Laboratory trials comparing a known susceptible Hairy Beggarticks biotype with this Hairy Beggarticks biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on Group B, C1/2, 5 resistant Hairy Beggarticks have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

Relative Fitness

Triazine resistant weeds often exhibit a lower relative fitness when compared to susceptible biotypes. The most common mutation conferring triazine resistance (Ser 264 to Gly mutation of the psbA gene) also causes a reduction in CO2 fixation, quantum yield, and seed and biomass production. There is no record in this database referring specifically to fitness studies on multiple resistant Hairy Beggarticks from Brazil.

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Brazil have been instrumental in providing you this information. Particular thanks is given to Nilda R. Burgos, Jamil Constantin, Rubem Oliveira, and Hudson Takano for providing detailed information.

In agricultural production systems where the glyphosate-resistant soybean crop (Glycine max) is grown and the practice of crop rotation with alternative herbicides is not adopted, the exclusive and continuous use of glyphosate has led to the occurrence of resistant weed populations that may limit or compromise the benefits of this technology. Thus, the efficacy of weed management programs, including the use of residual herbicides (sulfentrazone, flumioxazin, imazethapyr, diclosulan, chlorimuron and s-metolachlor) applied in preemergence and followed by in-crop postemergence applications of glyphosate (PRE-POST) were compared to glyphosate postemergence only programs - POST. The study was conducted across nine locations during the 2009/2010 and 2010/2011 growing seasons. PRE-POST programs were efficient in the control of Amaranthus viridis, Brachiaria plantaginea, Bidens pilosa, Commelina benghalensis, Eleusine indica, Euphorbia heterophylla and Raphanus raphanistrum, with the level of control being similar when comparing the program with two applications of glyphosate POST. Some PRE-POST programs were not efficient in controlling Cenchrus echinatus, Ipomoea hederifolia and Ipomoea triloba. Sulfentrazone and diclosulam PRE-POST programs improved the control of Ipomoea triloba compared to sequential applications of glyphosate alone. No significant differences in soybean yield were observed between any of the herbicide treatments or study locations. The use of residual herbicides in preemergence followed by glyphosate in-crop postemergence provides consistent weed control and reducing early season weed competition. Furthermore, these programs utilize at least two herbicide modes of action for herbicide use diversity, which will be needed to stay ahead of resistance build-up, regardless of when weeds may appear..

When herbicides with the same action mechanism are used repeatedly for several years, the herbicide resistant weeds can survive the treatment, propagate and dominate the area. The aim of this work was to identify and to map the patches of hairy beggarticks (Bidenspilosa) resistant to ALS inhibitors (acetolactate synthase) in the Mato Grosso do Sul region. Weed patch contour method was used to mapping, which is defined by walking around the weed patch. Hairy beggarticks biotypes were evaluated for their resistance to ALS inhibitors according to the increment on the doses of an herbicide on experimental field plot in the mapped area. The method used for hairy beggar ticks mapping by weed patch contour was considered effective under the evaluated conditions, and the geospatial weed map was obtained, allowing the patch spraying. There were areas of the field free of hairy beggar ticks. The studied field area was infested by hairy beggarticksbiotypes resistant to the applied herbicide, which was not efficient..

The presence of Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitors is a problem to weed management in cotton crop, due to the fact that few alternatives broadleaf selective herbicides area available. In order to supply this information gap, four experiments were established in greenhouse conditions with the objective of evaluating herbicides applied in post-emergence conditions, recommended either for conventional and transgenic cotton (resistant to glyphosate and amonio-glufosinate) for controlling these resistant biotypes. The experimental design was entirely randomized with four replications and 21 herbicides treatments, besides a check without herbicide application. Two experiments were conducted per species, where the first one corresponded to herbicides application in stages of two to four leaves, and the second in the stage of four to six. It was evaluated the percentage of control at 7 and 28 days after herbicide application. Amonio-glufosinate and glyphosate applied isolated or in combinations with other herbicides were effective in controlling B. pilosa independently of the growth stage. The two biotypes demonstrated to be highly resistant to ALS inhibitor herbicides. E. heterophylla showed greater sensitivity to herbicide amonio-glufosinate herbicide and glyphosate in early stages applications. Glyphosate stood out as a satisfactory alternative for controlling E. heterophylla. For this biotype, synergistic effect was verified for associations between amonio-glufosinate and pyrithiobac-sodium..

Bidens pilosa occurs in practically all the Brazilian territory, besides several other tropical habitats. This plant's most advantageous aspects in the competition with major annual and perennial cultivars are its abundant and long propagule production, preferential photo-blastism, water use efficiency, high nutrient extraction and use, and morphophysiological characteristics. Due to B. pilosas plasticity and adaptative flexibility, as well as interaction of the characteristics determining its competitiveness, it is difficult to identify those which are associated with higher competitive capacity and expressiveness. This species presents biotypes resistant to some herbicides, rendering its control difficult in agricultural areas. The use of other management methods is also difficult, due to the wide variation in the flow of propagule dissemination, germination and emergence, as well as the beneficial association of this weed with microorganisms present in the soil. Although this plant has aggressive infesting characteristics, this work has reported some mechanisms that can be used for its integrated management. B. pilosa also presents medical properties, with extensive scientific studies being necessary in order to obtain benefits..

Conyza bonariensis is one of the most important weeds in southern Brazil. The selection of biotypes tolerant and resistant to the herbicide glyphosate has led to increasing demand for alternatives of management strategy to control this species. This work aimed to evaluate the efficiency of different winter and summer management strategy for the control of Conyza bonariensis, by using glyphosate+2,4-D tank mixtures combined or not with residual herbicides. The different burndown alternatives were applied after corn harvest (winter burndown), associated to applications before soybean sowing (summer burndown) with a total of 15 treatments. Winter burndown options evaluated in this research were efficient in weed desiccation and provided excellent levels of residual weed control up to the next summer soybean pre-sowing. The sowing of oats after winter burndown with subsequent summer burndown with glyphosate+diclosulam+2,4-D was found to be efficient to control Bidens pilosa. Conyza bonariensis was totally controlled in all the burndown strategies in which the herbicide 2,4-D was associated to glyphosate..